Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
  • C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/041—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular fabrication or treatment of ingot or slab
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0426—Hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
  • C21D8/0436—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
  • C21D8/0463—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment following hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
  • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
  • C21D8/0473—Final recrystallisation annealing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/005—Ferrite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/009—Pearlite

Definitions

• the present invention relates to a steel sheet for cans and a manufacturing method thereof.
• the present invention particularly relates to a can steel sheet and a manufacturing method thereof suitable for being applied to a material for a can container used for food cans, beverage cans, and the like, and above all, a steel plate for cans excellent in strength and workability and the production thereof. Regarding the method.
• a steel sheet conventionally called a DR (Double Reduced) material may be used as a high-strength steel sheet for cans.
• the DR material is a steel sheet manufactured by performing cold rolling (secondary rolling) again after annealing. Although the DR material has high strength, it has a low elongation and is inferior in workability, so that it cannot be necessarily applied to a can body processed can that requires high workability and an easy open end that requires rivet processing.
• Patent Documents 1 and 2 propose a high-strength SR material having workability.
• Patent Document 1 C: 0.03 to 0.13%, Si: 0.03% or less, Mn: 0.3 to 0.6%, P: 0.02% or less, and Al: 0.1% or less, N: 0.012% or less, and further Nb: 0.005 to 0.05%, Ti: 0.005 to 0.05%, B: 0.0005 to 0.005%. It has a composition that contains at least one kind and the balance is iron and unavoidable impurities, and has a ferrite structure with a cementite ratio of 0.5% or more, and the average grain size of ferrite is 7 ⁇ m or less, and after coating baking treatment.
• a steel sheet for cans having a tensile strength of 450 to 550 MPa, a total elongation of 20% or more and a yield elongation of 5% or less has been proposed.
• Patent Document 2 by weight ratio, C: 0.020 to 0.150%, Si: 0.05% or less, Mn: 1.00% or less, P: 0.050% or less, S: 0.010. %, N: 0.0100% or less, Al: 0.100% or less, Nb: 0.005 to 0.025%, the balance consisting of unavoidable impurities and iron, and a substantial ferrite single-phase structure And a yield strength of 40 kgf / mm 2 or more, an average crystal grain size of 10 ⁇ m or less, and a plate thickness of 0.300 mm or less.
• a steel sheet for can manufacturing which has excellent surface properties after the can and has sufficient can strength.
• Patent Document 1 can be applied only to a steel plate having a tensile strength of up to 550 MPa, and cannot cope with further thinning. Further, the uniform elongation required for rivet workability is insufficient. Furthermore, the technique described in Patent Document 2 has a problem that it is not possible to achieve both high tensile strength of 550 MPa or more and sufficient elongation.
• the present invention has been made in view of such circumstances, and an object thereof is to provide a steel sheet for cans having high strength and excellent workability, and a method for manufacturing the same.
• the present invention has the following gist.
• C 0.085% or more and 0.130% or less, Si: 0.04% or less, Mn: 0.10% or more and 0.60% or less, P: 0.02% or less, S: more than 0.010% and 0.020% or less, Al: 0.02% or more and 0.10% or less, N: 0.0005% or more and 0.0040% or less, Nb: 0.007% or more and 0.030% or less, B: contains 0.0010% or more and 0.0050% or less, B / N, which is the ratio of the content (% by mass) of B to the content (% by mass) of N, is 0.80 or more, and the balance is a component composition consisting of Fe and inevitable impurities, Has a ferrite structure containing pearlite in an area fraction of 1.0% or more, A steel sheet for cans having a yield stress of 500 MPa or more, a tensile strength of 550 MPa or
• a pickling step of pickling the hot rolled plate after the winding step, A cold rolling step of cold rolling the hot rolled sheet after the pickling step under conditions of a rolling ratio of 85% or more,
• a method of manufacturing a steel sheet for cans
• the steel sheet for cans of the present invention has high strength and excellent workability. According to the present invention, it is possible to further reduce the thickness of a steel plate used for food cans, beverage cans, and the like, thereby achieving resource saving and cost reduction.
• composition of the can steel sheet of the present invention will be described.
• % indicating the content of each component means mass%.
• the can steel plate of the present invention is also simply referred to as a steel plate.
• C 0.085% or more and 0.130% or less C is an important element that contributes to the improvement of yield stress and tensile strength and the reduction of yield elongation and the improvement of uniform elongation due to the formation of pearlite.
• the C content is 0.085% or more
• the area fraction of pearlite in the steel sheet structure can be 1.0% or more
• the yield stress of the steel sheet can be 500 MPa or more
• the tensile strength can be 550 MPa or more. ..
• the C content is preferably 0.100% or more.
• the C content exceeds 0.130%, the solid solution C increases, so that the yield elongation increases and the uniform elongation also decreases. Therefore, the C content needs to be 0.130% or less.
• the C content is preferably 0.125% or less.
• Si 0.04% or less
• the content is required to be 0.04% or less.
• the Si content is preferably 0.03% or less.
• Si contributes to the improvement of the yield stress and the tensile strength, so it is preferable to add Si in an amount of 0.01% or more.
• Mn 0.10% or more and 0.60% or less Mn not only contributes to the improvement of yield stress and tensile strength by solid solution strengthening, but also promotes the formation of pearlite. As a result, work hardening is promoted, and in addition to tensile strength of 550 MPa or more, yield elongation of 5.0% or less and uniform elongation of 10% or more can be obtained. In order to obtain such an effect, the Mn content needs to be 0.10% or more. The Mn content is preferably 0.30% or more. On the other hand, when the Mn content exceeds 0.60%, not only the contribution to the formation of pearlite is saturated, but also the uniform elongation decreases due to excessive solid solution strengthening. Therefore, the upper limit of the Mn content needs to be 0.60%. The Mn content is preferably 0.55% or less.
• P 0.02% or less
• the upper limit of the P content is 0.02%.
• P contributes to the improvement of yield stress and tensile strength, so the P content is preferably 0.005% or more.
• the P content is more preferably 0.010% or more.
• S More than 0.010% and 0.020% or less S forms sulfides in steel and reduces hot rollability. Therefore, the S content is 0.020% or less. If the S content is 0.010% or less, pitting corrosion may occur depending on the contents of the can. Therefore, the S content needs to exceed 0.010%.
• Al 0.02% or more and 0.10% or less
• Al is useful as a deoxidizing element, and contributes to the reduction of yield elongation by forming a nitride. Therefore, Al needs to be contained at 0.02% or more.
• the Al content is preferably 0.03% or more.
• the Al content is preferably 0.08% or less.
• N 0.0005% or more and 0.0040% or less
• the N content is preferably 0.0035% or less.
• the lower limit of the N content is 0.0005%.
• Nb 0.007% or more and 0.030% or less
• Nb is an important element that improves yield stress and tensile strength by refining ferrite crystal grains and forming carbides, and in order to obtain such effects.
• the Nb content needs to be 0.007% or more.
• the Nb content is preferably 0.010% or more.
• the upper limit of the Nb content needs to be 0.030%.
• the Nb content is preferably 0.026% or less.
• B 0.0010% or more and 0.0050% or less
• B / N 0.80 or more
• B has the effect of forming BN with N to reduce the solid solution N and lowering the yield elongation.
• the B content needs to be 0.0010% or more.
• the B content is preferably more than 0.0020%.
• the ratio of the contents of B and N [content of B relative to content of N (mass%) (mass%) %)]]]] Is required to be 0.80 or more.
• B / N is preferably 1.00 or more, more preferably 1.20 or more.
• B / N is preferably 5.00 or less, and more preferably 3.00 or less, from the viewpoint of easily exhibiting better tensile properties. Further, even if B is contained excessively, not only the above effect is saturated, but also the uniform elongation is lowered, and the anisotropy is deteriorated to lower the workability. Therefore, the upper limit of the B content is It is necessary to set it to 0.0050%.
• the B content is preferably 0.0040% or less.
• the steel sheet for a can of the present invention may have a composition containing the above components and the balance being Fe and inevitable impurities.
• the steel sheet for a can of the present invention is, in addition to the above component composition, one or more selected from Ti: 0.005% to 0.030% and Mo: 0.01% to 0.05%. It is preferable to contain
• Ti 0.005% or more and 0.030% or less Ti has the effect of fixing N as TiN and lowering the yield elongation. Further, by preferentially producing TiN, the production of BN is suppressed, and by ensuring the solid solution B, the ferrite crystal grains are miniaturized to contribute to the improvement of the yield stress and the tensile strength. Further, the formation of fine carbide also contributes to the improvement of yield stress and tensile strength. Therefore, when Ti is contained, it is preferable to contain Ti in an amount of 0.005% or more. The Ti content is more preferably 0.010% or more.
• the Ti content of Ti exceeds 0.030%, the recrystallization temperature becomes excessively high, and it becomes difficult to achieve both tensile strength and uniform elongation. Therefore, when Ti is contained, the Ti content is preferably 0.030% or less. The Ti content is more preferably 0.020% or less.
• Mo 0.01% or more and 0.05% or less Mo contributes to the improvement of yield stress and tensile strength by refining ferrite crystal grains and forming carbides. Therefore, when Mo is contained, it is preferable to contain 0.01% or more of Mo.
• the Mo content is more preferably 0.02% or more.
• Mo when Mo is contained in excess of 0.05%, such effects are saturated and, in addition, grain boundary segregation becomes excessive and uniform elongation decreases. Therefore, when Mo is contained, the upper limit of the Mo content is preferably 0.05%.
• the structure of the steel sheet for a can of the present invention has a ferrite structure as a main phase, and the rest other than the pearlite has a ferrite structure (ferrite phase).
• the ferrite structure may include granular cementite.
• the sample used for observing the steel sheet structure is cut out from the steel sheet and embedded in resin so that the vertical cross section parallel to the rolling direction of the steel sheet can be observed.
• the structure was exposed by corroding with Nital, and the structure of the steel plate at 1/2 position of the plate thickness was photographed with a scanning electron microscope, and the area fraction of pearlite was image-processed.
• a steel sheet structure was photographed with a scanning electron microscope at a magnification of 3000 times in three randomly selected fields of view, and the area fraction of pearlite was measured by image processing from each SEM image, and the average value thereof was measured. Ask for.
• Yield stress 500 MPa or more, tensile strength: 550 MPa or more, yield elongation: 5.0% or less, uniform elongation: 10% or more
• the yield stress of steel sheet Of 500 MPa or more and the tensile strength of 550 MPa or more is preferably 510 MPa or more.
• the tensile strength is preferably 570 MPa or more.
• the upper limit of the yield stress is not particularly limited, but the yield stress is preferably 590 MPa or less from the viewpoint of the curl workability of the lid.
• the upper limit of the tensile strength is not particularly limited, but the tensile strength is preferably 650 MPa or less from the viewpoint of easy open end can openability. In order to prevent stretcher strain during can making or lid making, it is necessary to make the yield elongation 5.0% or less. The yield elongation is preferably 4.0% or less. In order to secure the neck / flange processability of the can body and the rivet processability of the easy open end, it is necessary to set the uniform elongation to 10% or more. The uniform elongation is preferably 12% or more. In addition, the elongation at break (EL) is preferably 15% or more. The elongation at break is more preferably 18% or more.
• the yield stress, tensile strength, uniform elongation, yield elongation, and elongation at break are measured according to JIS Z 2241 after taking JIS No. 5 tensile test pieces from the rolling direction and subjecting them to aging heat treatment at 210 ° C. for 20 minutes. evaluate.
• the yield stress is evaluated by the upper yield stress when there is an upper yield point, and by the 0.2% proof stress when there is no upper yield point.
• the uniform elongation is evaluated by the total elongation at the maximum test according to JIS Z2241.
• the plate thickness of the steel plate for a can of the present invention is not particularly limited, but 0.40 mm or less is preferable. Since the steel plate for a can of the present invention can be made extremely thin, it is more preferable to set the plate thickness to 0.25 mm or less from the viewpoint of resource saving and cost reduction.
• the plate thickness is preferably 0.10 mm or more.
• the steel plate for a can can be manufactured under the conditions described below.
• the steel plate for a can manufactured by the following manufacturing method may be appropriately subjected to a plating process such as Sn plating, Ni plating, and Cr plating, a chemical conversion treatment process, and a resin film coating process such as laminating.
• Heating temperature 1100 ° C or higher
• a steel slab having the above-mentioned composition is heated at a heating temperature of 1100 ° C or higher (heating step). If the heating temperature of the steel slab before hot rolling is too low, coarse nitrides may be generated and workability may deteriorate, so the heating temperature of the steel slab is set to 1100 ° C or higher.
• the heating temperature of the steel slab is preferably 1150 ° C. or higher. When Ti is contained, the heating temperature of the steel slab is more preferably 1200 ° C or higher. Further, the heating temperature of the steel slab is preferably 1280 ° C. or lower from the viewpoint of obtaining a better surface condition.
• the steel slab after the heating process is hot-rolled at a hot rolling finishing temperature of 830 ° C. or more and 940 ° C. or less (hot rolling process).
• hot rolling finishing temperature When the finishing temperature of hot rolling (hot rolling finishing temperature) becomes higher than 940 ° C, the ferrite crystal grains in the hot rolled sheet become coarse and the ferrite crystal grains after cold rolling, annealing and temper rolling become coarse. As a result, the yield stress and tensile strength decrease. In addition, the generation of scale may be promoted and the surface quality may deteriorate. Therefore, the upper limit of the hot rolling finishing temperature is 940 ° C.
• the upper limit of the hot rolling finishing temperature is preferably 920 ° C.
• the finishing temperature of the hot rolling is less than 830 ° C.
• coarse Nb carbide is formed during the hot rolling, and the yield stress and the tensile strength decrease. Therefore, the lower limit of the hot rolling finish temperature is set to 830 ° C.
• the preferable lower limit of the hot rolling finishing temperature is 850 ° C.
• Winding temperature 400 ° C. or more and less than 550 ° C.
• the hot rolled sheet obtained in the hot rolling step is wound at a winding temperature of 400 ° C. or more and less than 550 ° C. (winding step).
• the coiling temperature is 550 ° C. or higher
• cementite in the hot-rolled sheet is coarsened and stabilized, remains undissolved during annealing, and the pearlite fraction decreases.
• alloy carbides such as Nb carbides are coarsened to lower the yield stress and tensile strength. Therefore, the winding temperature needs to be lower than 550 ° C.
• the winding temperature is preferably 530 ° C or lower.
• the lower limit of the winding temperature is set to 400 ° C.
• the winding temperature is preferably 470 ° C. or higher.
• Rolling ratio 85% or more Cold rolling is performed on the hot-rolled sheet after the pickling process under conditions of a rolling ratio of 85% or more (cold rolling process).
• cold rolling By cold rolling, ferrite crystal grains after annealing are refined, and yield stress and tensile strength are improved.
• the rolling rate of cold rolling is set to 85% or more.
• the rolling rate is preferably 87% or more.
• the upper limit of the rolling rate of cold rolling is not particularly limited, but from the viewpoint of obtaining better workability, the rolling rate of cold rolling is preferably 93% or less.
• Annealing temperature 720 ° C. or more and 780 ° C. or less Annealing is performed on the cold-rolled sheet obtained in the cold rolling process under conditions of an annealing temperature of 720 ° C. or more and 780 ° C. or less (annealing process). It is important to form pearlite during the annealing process in order to obtain high tensile strength, large uniform elongation, and small yield elongation. Therefore, it is necessary to set the annealing temperature to 720 ° C or higher.
• the annealing temperature is preferably 730 ° C. or higher.
• the annealing temperature exceeds 780 ° C.
• alloy carbides such as Nb carbides are coarsened, and ferrite crystal grains are also coarsened to lower the yield stress and the tensile strength. Therefore, it is necessary to set the upper limit of the annealing temperature to 780 ° C.
• the annealing temperature is preferably 760 ° C or lower.
• the continuous annealing is preferable as the annealing method from the viewpoint of material uniformity.
• the annealing time is not particularly limited, it is preferably 15 s or more.
• the annealing time is preferably 60 s or less from the viewpoint of making the ferrite crystal grains fine.
• Elongation rate of temper rolling 0.5% or more and 5.0% or less
• the annealed plate obtained in the annealing step is rolled under the condition of an elongation rate of 0.5% or more and 5.0% or less (temper rolling step). ).
• the surface roughness is adjusted and the plate shape is corrected, and the strain is introduced into the steel plate to improve the yield stress and reduce the yield elongation.
• the lower limit of the rolling rate (stretching rate) of temper rolling is set to 0.5%.
• the elongation rate is preferably 1.2% or more.
• the upper limit of the elongation rate is set to 5.0%.
• the elongation rate is preferably 3.0% or less.
• JIS No. 5 tensile test pieces were taken from the steel sheet for cans along the rolling direction, and after aging heat treatment at 210 ° C. for 20 minutes, yield stress, tensile strength, uniform elongation, yield elongation, and break elongation were measured according to JIS Z 2241. evaluated. The evaluation results are shown in Table 3.
• the sample used for observing the steel plate structure is cut out from the steel plate for a can and embedded in a resin so that a vertical cross section parallel to the rolling direction of the steel plate can be observed, and the observation surface of the sample is polished and then corroded with a nital structure Appeared.
• the steel plate structure was photographed with a scanning electron microscope at a magnification of 3,000 times in three randomly selected visual fields at the 1/2 position of the plate thickness, and the area fraction of pearlite was measured by image processing from each SEM image. The average value was calculated. The measurement results are shown in Table 3.
• the yield stress is 500 MPa or more
• the tensile strength is 550 MPa or more
• the uniform elongation is 10% or more
• the yield elongation is 5.0% or less. Therefore, it is a high-strength can steel sheet with high uniform elongation and low yield elongation.
• one or more of the yield stress, the tensile strength, the uniform elongation, and the yield elongation was inferior.

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